Multiple ratio power transmission mechanism with an infinitely variable overdrive range

ABSTRACT

A multiple ratio power transmission mechanism for use in an automotive vehicle driveline comprising planetary gear units and clutch and brake structure for controlling the relative motion of the elements of the gear units to establish multiple torque ratios including a direct drive ratio and an underdrive ratio, and an infinitely variable overdrive unit having an input portion connected to one element of said gearing, an output portion connected to the power output shaft for the transmission mechanism and a reaction portion adapted to be selectively braked whereby the output shaft may be overdriven with respect to the input shaft throughout a predetermined range of ratios, the lower ratio of the range being close to unity whereby the driveline may be adapted to accommodate varying road loads without frequency upshifting and downshifting between the overdrive range and the direct-drive range.

tlnited States Patent 91 Lemieux Get, 16, 1973 [75] Inventor: George E.Lemieux, Livonia,

Mich. [73] Assignee: Ford Motor Company,

Dearborn, Mich. [22T Filed: Apr. 26, 1971 [21] Appl. No.: 137,374

[52] 11.8. C1. 74/690, 74/759 [51] Int. Cl. Fl6h 37/06, F16h 57/10 [58]Field of Search 74/690, 691

[56] References Cited UNITED STATES PATENTS 2,093,236 9/1937 Dodge etal. 74/691 X 3,238,816 3/1966 Schottler 74/690 3,244,025 4/1966Francisco 74/690 3,494,224 2/1970 Fellows et a1... 74/691 3,545,30212/1970 Schofield Primary ExaminerCharles J. Myhre AssistantExaminer-Thomas C. Perry Attorney-John R. Faulkner and Donald J.Harrington ABSTRACT A multiple ratio power transmission mechanism foruse in an automotive vehicle driveline comprising planetary gear unitsand clutch and brake structure for controlling the relative motion ofthe elements of the gear units to establish multiple torque ratiosincluding a direct drive ratio and an underdrive ratio, and aninfinitely variable overdrive unit having an input portion connected toone element of said gearing, an output portion connected to the poweroutput shaft for the transmission mechanism and a reaction portion.

adapted to be selectively braked whereby the output shaft may beoverdriven with respect to the input shaft throughout a predeterminedrange of ratios, the lower ratio of the range being close to unitywhereby the driveline may be adapted to accommodate varying road loadswithout frequency upshifting and downshifting between the overdriverange and the directdrive range.

4 Claims, 4 Drawing Figures GENERAL DESCRIPTION OF THE INVENTION Theimprovements of my invention are adapted to be used in a multiple ratio,geared, power transmission mechanism in an automotive vehicle driveline.It includes an infinitely variable drive having power input portions andpower output portions connected to separate elements of the gear system.It also includes a reaction element which may be braked selectively whenoverdrive operation is desired.

Multiple underdrive ratios are achieved by controlling the relativemotion of the elements of the gear system with clutches and brakes inthe usual fashion. The overdrive speed range is provided by establishinga compound torque flow path through the gear system and the overdriveunit so that the driven shaft of the transmission mechanism isover-speeded with respect to the input shaft. The overall torque ratiorange can be varied when the overdrive unit is active by varying theratio of the overdrive unit. Compensation thus can be made for changesin road load without the necessity for downshifting the transmission tothe direct drive range.

In the particular embodiment of this disclosure, the overdrive unit is aball friction drive in which the adjustable outer races are connected toone portion of the gear system and the carrier is connected to another.Adjustable inner races may be braked to provide a reaction point for thegear system. The elements of the overdrive unit thus cooperate bothfunctionally and structurally with the individual elements of the gearunits to produce an overdrive ratio range in which the overdrive ratiocan be varied from a valueclose to or equal to unity to a limitingoverdrive speed ratio. Suitable controls may be used for varying theratio of the overdrive unit in response to changing driving conditions.Vehicle upshifting and down-shifting between the overdrive range and thedirect drive ratio is avoided.

The overdrive function is introduced into the transmission systemwithout requiring the addition of more than one releasable frictiontorque member.

The gear system of my improved mechanism has portions that are common tothe well known Simpson gear system in which two simple planetary gearunits form three forward driving torque flow paths and a single reversetorque flow path. The sun gears of the two gear units are connectedtogether or are formed integrally. The carrier of the first unit isconnected to the driven shaft as well as to the carrier for theoverdrive unit. The carrier for the second gear unit acts as a reactionmember during low speed ratio operation. The sun gears, which are brakedwith a separate intermediate speed ratio brake, act as a reaction pointfor the transmission during intermediate speed ratio operation.

The sun gears are connected to the adjustable outer races of theinfinitely variable unit. The ring gear of the second gear unit isconnected to the power output shaft through the carrier for theoverdrive unit.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWING FIG. I shows inschematic form a geared transmission including an overdrive mechanismwith an infinitely variable ratio characteristic;

FIG. 2 is a chart showing the clutch and brake engagement and releasepattern for the mechanism of FIG. 1;

FIG. 3 is a chart showing the speeds of the various elements ofthemechanism in FIG. 1 relative to the speed of the power input shaft;

FIG. 4 is a diagram showing the geometric relationship of the torquetransmitting balls and the cooperating inner and outer races of theinfinitely variable mechanism of FIG. 1.

PARTICULAR DESCRIPTION OF THE INVENTION In FIG. 1 numeral 10 designatesa hydrokinetic torque converter comprising bladed impeller 12, a bladedturbine 14 and a bladed stator 16. The impeller, the turbine and thestator are arranged in toroidal fluid flow relationship. The impeller isdriven by an engine crankshaft shown schematically at 18. The bladedstator is supported on a stationary sleeve shaft 20. An overrunningbrake 22 anchors the stator 16 against rotation in adirection oppositeto the direction of rotation of the impeller but permits free-wheelingmotion of the stator in the direction of rotation of the impeller duringcoupling operation.

Turbine 14 is connected to turbine shaft 24. It serves as a torque inputshaft for the gear system, which comprises a first simple planetary gearunit 26 and a second simple planetary gear unit 28. 7

Gear unit 26 includes ring gear 30, sun gear 32, carrier 34 and planetpinions 37 mounted on the carrier 34 in meshing engagement with the sungear 32 and the ring gear 30. The gear unit 28 is similar to gear unit26. It includes ring gear 36, sun gear 38, carrier 40 and planet pinions42 journalled on the carrier 40 in meshing engagement with the sun gear38 and the ring gear 36. Sun gears 32 and 38 are joined together orformed integrally so that they rotate in unison.

A direct drive and reverse clutch 44 is adapted to connect selectivelythe shaft 24 to the sun gears. It is applied during operation in thedirect-drive, third speed ratio and during reverse drive operation. Thedriven member of the clutch 44 comprises a drum 46 about which ispositioned brake band 48. The brake band 48 is applied during operationin intermediate speed ratio, thus anchoring the sun gear 32 so that itacts as a reaction element during second speed ratio underdriveoperation.

A forward drive clutch 50 is adapted to provide selectively a connectionbetween shaft 24 and ring gear 30. It is applied during operation ineach of the forward driving ratios. Carrier 34 and ring gear 36 areconnected to power output shaft 52. The connection between ring gear 36and the shaft 52 is through the carrier 54 of an infinitely variablefriction drive mechanism 56.

Carrier 40 of the planetary gear unit 28 is connected to brake drum 58.Brake band 60 circles drum 58 and is adapted to be applied duringoperation in the low speed ratio, thus providing a reaction point. Brakeband '60 is complemented by overrunning brake 62 which distributesreaction torque to the transmission housing during low speed ratiooperation. Brake band 60 is used during reverse drive and during hillbraking operation in the low speed ratio.

The infinitely variable friction drive mechanism 56 includes a pluralityof friction drive balls 64 which are journalled rotatably on carrier 54.Outer races 66 engage balls 64 and inner races 67 similarly engage balls64 at a relatively inwardly spaced location. Races 67 are adapted to beanchored by brake band 68 which surrounds brake drum 70 connecteddirectly to the inner races 67. Reference may be made to U.S. Pat. No.3,203,278 for a particular description of the mode of operation of afriction drive mechanism similar to that shown at 56.

The races 66 may be moved toward each other and away from each other byfluid pressure operated servos so that the points of contact of theballs with the races will vary from one limiting radial position to asecond, radially outward position. The same is true for the races 67.These also may be advanced and retracted with respect to each other sothat the points of contact between the races and the balls will beadjusted radially. The radial variation of the location of the points ofcontact of the balls with respect to the inner and outer races causes achange in the speed ratio of the driving and driven portions of thefriction drive mechanism.

The geometric relationship between the balls and the inner and outerraces is shown in FIG. 4. The surface of contact between the balls andthe races is a curved surface of predetermined contour. The angle (1,,indicated in FIG. 4 is the angle between a horizontal reference line anda point drawn between the point of contact between the race and the balland the center of the ball. In a preferred embodiment the maximum angleformed as the point of contact moves inwardly is 24". At the otherlimiting position of the race 66 the angle a is 65. This produces anoverdrive ratio of 1.23 to 2.20.

The clutch and brake engagement and release pattern necessary toaccomplish various ratio changes is shown in FIG. 2. To establish lowspeed ratio operation, clutch 50 is applied. It remains applied duringoperation in each of the other forward driving ratios. Torque then isdelivered to the ring gear 30. The resistance to rotation offered bycarrier 34 causes reaction torque to be delivered to sun gear 32 and sungear 38. Carrier 40 is prevented from rotating in a reverse direction bybrake 62 thereby causing forward motion of the ring gear 36. Thisforward motion is distributed to the output shaft 52, thus providing asecond torque delivery path that complements the torque delivery paththrough the first gear unit 26. If manual low operation or hill brakingis desired, the brake band is applied so that the carrier 40 canaccommodate reaction torque in the opposite direction.

Intermediate speed ratio operation is achieved by engaging brake band48. This anchors the sun gear 32 causing carrier 34 to rotate at anincreased speed ratio as the sun gear 32 acts as a reaction point.Overrunning brake 62 freewheels at this time, thereby rendering the gearunit inactive.

Direct drive operation is achieved by engaging simultaneously clutches44 and 50. All the elements of the gear system rotate together in unisonto establish a 1:1 driving ratio.

Reverse drive operation is achieved by releasing clutch 50 and applyingclutch 44. Brake band 60 is applied. Turbine torque then is delivereddirectly to the sun gear 38. Since the brake band 60 anchors the carrier40, ring gear 36 is driven in a reverse direction thereby driving theoutput shaft 52 in a reverse direction.

A change in the operating mode to the overdrive condition is effected byapplying brake band 68. This anchors the inner races 67 of theinfinitely variable friction drive mechanism 56. Since the inner racesnow serve as a reaction point and since the carrier 34 drives carrier54, the outer races 66 are overdriven thereby causing an effectiveincrease in the overall speed ratio. The torque applied to the outerraces 66 by the sun gear 32 is opposite to the direction of the torquedistributed to the shaft 52 by the carrier 34. The net torquedistributed to the shaft 52 is the difference between the torquedistributed to the carrier 54 through races 66 and the torquedistributed to the shaft 52 by the carrier 34. Thus, the effectivetorque in shaft 52 is less than the effective turbine torque in shaft24. Since that is the case, it necessarily follows that the speed of theshaft 52 is greater than the speed of the shaft 24.

In FIG. 3 l have illustrated the speeds of the various elements of thegear system of FIG. 1 with respect to the speed of the input shaft.During direct drive operation the speed of the driven shaft relative tothe speed of the driving shaft is 1.00 times input speed. The lowestspeed ratio available in the overdrive range is 1.1 17 times inputspeed. Thus, the lowest overdrive ratio in the overdrive range is almostequal to the direct drive ratio. The overdrive ratio can be varied up to2.215 merely by varying the speed ratio of the infinitely variablefriction drive mechanism.

Having thus described a preferred form of my invention, what I claim anddesire to secure by U.S. Letters Patent is:

l. A power transmission mechanism having multiple underdrive speedratios, a direct drive ratio and an overdrive range comprising planetarygear units having power input portions, power output portions and torquereaction portions, clutch means for connecting selectively the powerinput portions of the gear units to a driving shaft, the power outputportions of the gear units being connected to a driven shaft, brakemeans for selectively anchoring said reaction portions, an infinitelyvariable overdrive unit comprising a torque input member connected tosaid torque reaction portions and a torque output member connected tosaid driven shaft, a third member of said infinitely variable overdriveunit being adapted to absorb torque reaction, and overdrive brake meansfor anchoring said third member of said overdrive unit.

2. The combination as set forth in claim 1 wherein said gear units firstand second simple planetary gear units each has a ring gear, a sun gear,a carrier and planet pinions journalled on said carrier in meshingengagement with said sun and ring gears, said clutch means including twoseparately operable clutches, a first of said clutches being adapted toestablish a driving connection between said driving shaft and the ringgear of a first of said gear units, a second of said clutches beingadapted to selectively establish a driving connection between the sungears of said gear units and said driving shaft, said sun gears beingconnected together, the carrier of said first gear unit being connectedto said driven shaft, the ring gear of said second gear unit beingconnected to the torque output portion of said overdrive unit, the inputportion of said overdrive unit being connected to said sun gears, saidtorque output portion of said overdrive unit being connected to saiddriven shaft, means for selectively anchoring the carrier of said secondgear unit during low driven shaft and means for varying the radialposition of the points of contact of said races with said balls.

4. The combination as set forth in claim 2 wherein said overdrive unitcomprises a ball friction drive having a series of torque transmittingballs, inner races and outer races frictionally contacting said balls, acarrier journalling said balls for rotation about their axes, saidcarrier for said overdrive unit being connected to said driven shaft andmeans for varying the radial position of the points of contact of saidraces with said balls.

I "3 765370 Dated IJNITED sTATEs PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. October 16, 1973 Inventor) George E. Lemieux It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 4, line 19, after "gear units" insert ---comprise--.

Signed and sealed this 16th day of July 1971 (SEAL) Attest:

MCCOY n. GIBSON, I JR. I I c. MARSHALL DANN Attestlng OfficerCommissioner of Patents USCOMM-DC 60376-P69 U,S. GOVERNMENT PRINTINGOFFICE: I969 0-366-334 FORM PO-IOSO (10-69)

1. A power transmission mechanism having multiple underdrive speedratios, a direct drive ratio and an overdrive range comprising planetarygear units having power input portions, power output portions and torquereaction portions, clutch means for connecting selectively the powerinput portions of the gear units to a driving shaft, the power outputportions of the gear units being connected to a driven shaft, brakemeans for selectively anchoring said reaction portions, an infinitelyvariable overdrive unit comprising a torque input member connected tosaid torque reaction portions and a torque output member connected tosaid driven shaft, a third member of said infinitely variable overdriveunit being adapted to absorb torque reaction, and overdrive brake meansfor anchoring said third member of said overdrive unit.
 2. Thecombination as set forth in claim 1 wherein said gear units first andsecond simple planetary gear units each has a ring gear, a sun gear, acarrier and planet pinions journalled on said carrier in meshingengagement with said sun and ring gears, said clutch means including twoseparately operable clutches, a first of said clutches being adapted toestablish a driving connection between said driving shaft and the ringgear of a first of said gear units, a second of said clutches beingadapted to selectively establish a driving connection between the sungears of said gear units and said driving shaft, said sun gears beingconnected together, the carrier of said first gear unit being connectedto said driven shaft, the ring gear of said second gear unit beingconnected to the torque output portion of said overdrive unit, the inputportion of said overdrive unit being connected to said sun gears, saidtorque output portion of said overdrive unit being connected to saiddriven shaft, means for selectively anchoring the carrier of said secondgear unit during low speed ratio operation, and other brake means foranchoring the sun gears during intermediate speed ratio operation, bothclutches being applied during direct drive operation, the second clutchbeing released and said overdrive brake means being applied duringoverdrive operation.
 3. The combination as set forth in claim 1 whereinsaid overdrive unit comprises a ball friction drive having a series oftorque transmitting balls, inner races and outer races frictionallycontacting said balls, a carrier journalling said balls for rotationabout their axes, said carrier for said overdrive unit being connectedto said driven shaft and means for varying the radial position of thepoints of contact of said races with said balls.
 4. The combination asset forth in claim 2 wherein said overdrive unit comprises a ballfriction drive having a series of torque transmitting balls, inner racesand outer races frictionally contacting said balls, a carrierjournalling said balls for rotation about their axes, said carrier forsaid overdrive unit being connected to said driven shaft and means forvarying the radial position of the points of contact of said races withsaid balls.